Editing Snowball Earth (section)

===Low-latitude glacial deposits===
[[Image:PocatelloFm.JPG|thumb|[[Diamictite]] of the [[Neoproterozoic]] Pocatello Formation, a "snowball Earth"-type deposit]]
[[File:Elatina Fm diamictite.JPG|thumb|Elatina Fm [[diamictite]] below [[Ediacaran]] [[Global Boundary Stratotype Section and Point|GSSP]] site in the [[Flinders Ranges National Park|Flinders Ranges NP]], South Australia. [[Australian one dollar coin|A$1 coin]] for scale.]]
Sedimentary rocks that are deposited by glaciers have distinctive features that enable their identification. Long before the advent of the snowball Earth hypothesis, many Neoproterozoic sediments had been interpreted as having a glacial origin, including some apparently at tropical latitudes at the time of their deposition. However, many sedimentary features traditionally associated with glaciers can also be formed by other means.<ref name=Arnaud2002>{{cite journal
| author = Arnaud, E.
| author2 = Eyles, C. H.
| year = 2002
| title = Glacial influence on Neoproterozoic sedimentation: the Smalfjord Formation, northern Norway
| journal = Sedimentology
| volume = 49
| issue = 4
| pages = 765–88
| doi = 10.1046/j.1365-3091.2002.00466.x
| bibcode = 2002Sedim..49..765A
| s2cid = 128719279
}}</ref> Thus the glacial origin of many of the key occurrences for snowball Earth has been contested.<ref name="Eyles2004" />
As of 2007, there was only one "very reliable"—still challenged<ref name="Eyles2004" />—datum point identifying tropical tillites,<ref name="Evans" /> which makes statements of equatorial ice cover somewhat presumptuous. However, evidence of sea-level glaciation in the tropics during the Sturtian glaciation is accumulating.<ref name='Macdonald2010'>{{cite journal |last1=Macdonald |first1=F. A. |last2=Schmitz |first2=M. D. |last3=Crowley |first3=J. L. |last4=Roots |first4=C. F. |last5=Jones |first5=D. S. |last6=Maloof |first6=A. C. |last7=Strauss |first7=J. V. |last8=Cohen |first8=P. A. |last9=Johnston |first9=D. T. |last10=Schrag |first10=D. P. |title=Calibrating the Cryogenian |journal=Science |date=4 March 2010 |volume=327 |issue=5970 |pages=1241–1243 |doi=10.1126/science.1183325 |bibcode=2010Sci...327.1241M |pmid=20203045|s2cid=40959063 }}</ref><ref>{{cite journal |last1=Kerr |first1=R. A. |title=Snowball Earth Has Melted Back To a Profound Wintry Mix |journal=Science |date=4 March 2010 |volume=327 |issue=5970 |pages=1186 |doi=10.1126/science.327.5970.1186 |pmid=20203019 |bibcode=2010Sci...327.1186K |doi-access=free }}</ref>
Evidence of possible glacial origin of sediment includes:
* [[Dropstones]] (stones dropped into marine sediments), which can be deposited by glaciers or other phenomena.<ref name=Donovan1997>{{cite journal
| author = Donovan, S. K.
| author2 = Pickerill, R. K.
|year = 1997
| title = Dropstones: their origin and significance: a comment
| journal = Palaeogeography, Palaeoclimatology, Palaeoecology
| volume = 131
| issue = 1
| pages = 175–8
| doi = 10.1016/S0031-0182(96)00150-2
| bibcode = 1997PPP...131..175D
}}</ref>
* [[Varves]] (annual sediment layers in periglacial lakes), which can form at higher temperatures.<ref name=Thunell1995>{{cite journal
| author1 = Thunell, R. C.|author-link1=Robert Thunell
| author2 = Tappa, E.
| author3 = Anderson, D. M.
| date = 1 December 1995
| title = Sediment fluxes and varve formation in Santa Barbara Basin, offshore California
| journal = Geology
| volume = 23
| issue = 12
| pages = 1083–6
| doi = 10.1130/0091-7613(1995)023<1083:SFAVFI>2.3.CO;2
|bibcode = 1995Geo....23.1083T }}</ref>
* [[Glacial striation]]s (formed by embedded rocks scraped against bedrock): similar striations are from time to time formed by [[mudflow]]s or tectonic movements.<ref name=Jensen1996>{{cite journal
| author = Jensen, P. A.
| author2 = Wulff-pedersen, E.
| date = 1 March 1996
| title = Glacial or non-glacial origin for the Bigganjargga tillite, Finnmark, Northern Norway
| journal = Geological Magazine
| volume = 133
| issue = 2
| pages = 137–45
| doi = 10.1017/S0016756800008657
| bibcode = 1996GeoM..133..137J
| s2cid = 129260708
}}</ref>
* [[Diamictite]]s (poorly sorted conglomerates). Originally described as glacial [[till]], most were in fact formed by [[debris flow]]s.<ref name=Eyles2004>{{cite journal
| author = Eyles, N.
| author2 = Januszczak, N.
| year = 2004
| title = 'Zipper-rift': A tectonic model for Neoproterozoic glaciations during the breakup of Rodinia after 750 Ma
| journal = Earth-Science Reviews
| volume = 65
| issue = 1–2
| pages = 1–73
| doi = 10.1016/S0012-8252(03)00080-1
| bibcode=2004ESRv...65....1E
}}</ref>